The field of bioinformatics is what we would call for using molecular data to understand more about organisms in different environments (including extreme environments). There are a number of free or relatively cheap courses online that can be used to start (Udemy has a course here.) If you search for "bioinformatic courses online" on google you should find some. Most molecular data is placed on open source repositories meaning they are available to everyone. Other datasets as mentioned in the other post can sometimes be hard to acquire not through an institution, but this is changing slowly to be more open I would say.

Many questions can be answered using this data, I would say the difficult thing is defining the question - there is so much data it is easy to get lost when exploring it. You might be interested in understanding if x species of bacteria is affected by temperature, or if the total microbial community is different between different kinds of ice - these are all things you could answer with this data.